The present invention relates in general to sub-sea oil well drilling apparatus wherein a drilling template is positioned on a sea bottom surface to provide a stable reference surface for well drilling tools and other well-head assemblies which are lowered onto the template from a sea surface drilling platform or drilling ship. In particular, the present invention relates to apparatus for guiding the drilling tools and other well-head assemblies onto the template as the tool or assembly is lowered from a drilling platform or ship and landed on the template. Further, the present invention also relates to apparatus for selectively positioning the drilling tool or assembly relative to the template once the tool or assembly has been landed on the template.
Heretofore, sub-sea drilling templates have provided relatively few drilling sites for any given template. The drilling tools or well head assemblies have been lowered from the drilling platform or drilling ship on the end of a drill caseing and have been guided into position on the template by wire line guide cables affixed to the template and extending to the drilling platform or ship. To reposition the tool or well head assembly at another site on the template, the tool or assembly was raised to the surface and guided down another set of guide cables to the second drilling site.
These prior solutions to the problem of multiple well production installations have resulted in production time losses due to the excessive vertical distances through which the tool or well head assembly must be moved in order to effect a relatively small lateral displacement at the template.
Additionally, the presence of a multitude of guide cables extending from the template to the surface clutters the sea zone between the template and the drilling platform or ship and increases the difficulty of disconnecting a drilling ship from the sub-sea installation during sever storms or other adverse circumstances.